Saphenous vein grafts will be interimposed at a 90 degrees proximal angle between the right and left external iliac arteries in small animals. Animals will be grouped according to the degree of stenosis present in the bypassed artery and will be studied in equal groups either four months or eight months after graft implantation. Using a pulsed ultrasonic Doppler, the velocity of flow will be measured at different sites along the vein graft. The volume of flow and arterial pressure in each branch of the model will also be recorded. Labelled albumin uptake studies and microscopic examination of the vein wall will be performed. The hemodynamic data will be correlated with albumin uptake, the histological and biochemical findings. Using these results, the role of wall shear rates in the development of intimal proliferation in autologous saphenous vein grafts will be analyzed.